How exactly would I kill my Tomogunchi? It reset entirely after I got the dragon, so I had to go through the process all over again and I got a horse. I'm not wanting the horse if I'm being honest.
To reset the creature you will need to complete its cycle to reset it back to an egg. The pony came up because of average care. You could evolve the pony to its secret form but sounds like you want to restart. You can complete the adult cycle by filling the bonus meter at the bottom of the screen and banking it by using the watch gesture. To earn bonus time for an adult: Winning matches + top 3 placement; (2) instances of a win + top 3 placement fill the bonus meter. Or you can equip another watch and let it die.